Dynamic Write-Current Control for Disk Drive Head
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Solution Overview
Problem
Current magnetic data storage systems face challenges in minimizing track erasure due to adjacent track interference and stray magnetic fields, particularly when writing data with varying frequencies and patterns, as existing solutions like look-back algorithms are inadequate for adjusting overshoot currents effectively.
Innovation Solution
The implementation of a Channel-Preamp Dynamic Wave Shape (CP-DWS) system that dynamically adjusts the write driver's signal wave-shape based on write data patterns using amplitude-level modulation (AML), allowing for look-ahead, look-back, or combined strategies to control overshoot amplitude, thereby optimizing write current and reducing cross-track interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If write current overshoot amplitude is increased to ensure peak current reaches target before next magnetic transition, then recording performance is improved, but adjacent track erasure and cross-track interference increase
Solution Approach 1:
The patent implements dynamic write current overshoot amplitude control that adjusts the overshoot level based on the specific data pattern being written. The system transitions from static to dynamic control by using look-ahead detection of data patterns (such as long magnets followed by frequent transitions) to selectively apply higher or lower overshoot amplitudes, optimizing recording performance while minimizing adjacent track interference for each specific writing scenario
Solution Approach 2:
The patent changes the parameter of write current overshoot amplitude dynamically based on data pattern detection. By detecting specific patterns like long magnets followed by frequent transitions using look-ahead logic, the system adjusts the overshoot amplitude parameter to match the recording requirements, thereby improving recording performance while reducing unnecessary adjacent track erasure that occurs with fixed high overshoot settings
2Adaptability or versatility
If look-back algorithm is used to adjust overshoot current based on previous bits, then some pattern compensation is achieved, but it cannot effectively adjust overshoot for first transition in dibit or transitions preceding long magnets
Solution Approach 1:
The patent applies look-ahead detection to identify data patterns before writing occurs. By detecting patterns such as long magnets followed by frequent transitions in advance, the system can pre-adjust the overshoot amplitude settings before the actual writing takes place, enabling effective compensation for transitions that look-back algorithms cannot handle, including the first transition in a dibit and transitions preceding long magnets
3Productivity
If write current is optimized for frequent transitions, then short magnet recording is improved, but long magnet sections suffer from insufficient field strength and adjacent track interference increases
Solution Approach 1:
The patent implements dynamic adjustment of overshoot amplitude based on detected data patterns. When long magnet sections followed by frequent transitions are detected using look-ahead logic, the system selectively reduces overshoot amplitude during the long magnet writing portion while maintaining adequate field strength for subsequent frequent transitions, thereby simultaneously improving both long and short magnet recording while reducing cross-track interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise control of write current overshoot, minimizing track erasure and maximizing areal density by adjusting overshoot amplitude based on subsequent data bits, reducing cross-track interference and improving recording performance.
Implementation Method 1
The write driver preamp 18 generates an analog current signal that is applied to the inductive coil in the write head 15 to write data by selectively magnetizing portions of the magnetic material on the surface of the rotating disk and creating magnetic transitions
Data Source
AI summary
Disk drives with a Channel System and Write Driver Preamp architecture that dynamically adjusts the write driver's signal wave-shape depending on the write data signal pattern are described. The wave-shape control signal is generated in the Channel and transmitted to the Write Driver Preamp. Embodiments of the invention provide discrete n-level overshoot amplitude control using amplitude-level modulated (AML) signal. One embodiment implements a look-ahead strategy overshoot amplitude control where the overshoot amplitude for each transition depends only on the subsequent (following) bits in the data stream and not on any previously recorded data.